在UIPageViewController中获取用户滑动方向

  • Z时代
  • 2024-01-10
  • 分类：问答

这两种方法viewControllerBeforeViewController以及viewControllerAfterViewController的两种方法UIPageViewControllerDataSource都不会告诉您滑动的方向。

该方法transitionCompleted的的UIPageViewController委托不帮助我们，所以尽管。它只是告诉页面是否被完全刷了。

那么我应该使用哪种方法来准确地检测用户方向（左或右）？

这两个属性可能会有所帮助：

let directionForward = UIPageViewControllerNavigationDirection.Forward
let directionReverse = UIPageViewControllerNavigationDirection.Reverse

我的代码如下所示：

import UIKit
class ProView: UIViewController, UIPageViewControllerDataSource, UIPageViewControllerDelegate {
var pageViewController: UIPageViewController?
let characterImages = ["character1", "character2", "character1", "character2", "character1", "character2", "character1", "character2"]
override func viewDidLoad() {
    super.viewDidLoad()
    createPageViewController()
    setupPageControl()
    character = 1
}
override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
}
// Forward, check if this IS NOT the last controller
func pageViewController(pageViewController: UIPageViewController,
    viewControllerAfterViewController ProView: UIViewController) -> UIViewController? {
        let itemController = ProView as PageItemController
        // Check if there is another view
        if itemController.itemIndex+1 < characterImages.count {
            return getItemController(itemController.itemIndex+1)
        }
        return nil
}
// Check if this IS NOT the first controller
func pageViewController(pageViewController: UIPageViewController,
    viewControllerBeforeViewController ProView: UIViewController) -> UIViewController? {
    let itemController = ProView as PageItemController
        if itemController.itemIndex < 0 {
            return getItemController(itemController.itemIndex-1)
        }
        return nil
}
private func getItemController(itemIndex: Int) -> PageItemController? {
    if itemIndex < characterImages.count {
        let pageItemController = self.storyboard!.instantiateViewControllerWithIdentifier("ItemController") as PageItemController
        pageItemController.itemIndex = itemIndex
        pageItemController.imageName = characterImages[itemIndex]
        return pageItemController
}
    return nil
}
func createPageViewController() {
    let pageController = self.storyboard!.instantiateViewControllerWithIdentifier("PageController") as UIPageViewController
    pageController.dataSource = self
    pageController.delegate = self
    if characterImages.count > 0 {
        let firstController = getItemController(0)!
        let startingViewControllers: NSArray = [firstController]
        pageController.setViewControllers(startingViewControllers, direction: UIPageViewControllerNavigationDirection.Forward, animated: false, completion: nil)
    }
    pageViewController = pageController
    addChildViewController(pageViewController!)
    self.view.addSubview(pageViewController!.view)
    pageViewController?.didMoveToParentViewController(self)
}
func setupPageControl() {
    let appearance = UIPageControl.appearance()
    appearance.pageIndicatorTintColor = UIColor.grayColor()
    appearance.currentPageIndicatorTintColor = UIColor.whiteColor()
}
func presentationCountForPageViewController(pageViewController: UIPageViewController) -> Int {
    return characterImages.count
}
func presentationIndexForPageViewController(pageViewController: UIPageViewController) -> Int {
}
// BETA
func pageViewController(PageItemController: UIPageViewController,
    didFinishAnimating finished: Bool,
    previousViewControllers pageViewController: [AnyObject],
    transitionCompleted completed: Bool)
{
    if (!completed)
    {
        // You do nothing because whatever page you thought
        // the book was on before the gesture started is still the correct page
        return;
    }
    // This is where you would know the page number changed and handle it appropriately
    character = workaround
    }
}
class PageItemController: UIViewController {
@IBOutlet weak var imageCharacterChoose: UIImageView!
var itemIndex: Int = 0
var imageName: String = "" {
    didSet {
        if let imageView = imageCharacterChoose {imageCharacterChoose.image = UIImage(named: imageName)
        }
    }
}
}

根据pbasdf所说，

var currentIndex: Int = 0
var nextIndex: Int = 0
func pageViewController(PageItemController: UIPageViewController,
    willTransitionToViewControllers pageViewController: [AnyObject]) {
        //                          pageViewController is the pending View Controller
        nextIndex = currentIndex
        // pageViewController...... how do I get its index?
}

回答：

您应该同时使用willTransitionToViewControllers:和didFinishAnimating:委托方法来确定转换是向前还是向后。在课程开始时声明几个索引变量，例如currentIndex和nextIndex（均为Int）。

在该willTransitionToViewControllers方法中，将nextIndex等于itemIndex挂起的视图控制器的：

func pageViewController(pageViewController: UIPageViewController, willTransitionToViewControllers pendingViewControllers: [AnyObject]) {
    // the page view controller is about to transition to a new page, so take note
    // of the index of the page it will display.  (We can't update our currentIndex
    // yet, because the transition might not be completed - we will check in didFinishAnimating:)
    if let itemController = pendingViewControllers[0] as? PageItemController {
        nextIndex = itemController.itemIndex
    }
}

您可以在此时确定转换是前进还是后退：如果nextIndex> currentIndex，则前进；如果nextIndex<

currentIndex则向后。然后在中didFinishAnimating，如果completed为true（因此它完成了向下一个视图控制器的转换），请将其设置currentIndex为，nextIndex以便您可以currentIndex在需要指示屏幕上当前页面的任何位置使用：

func pageViewController(pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [AnyObject], transitionCompleted completed: Bool) {
    if (completed) {
        // the page view controller has successfully transitioned to the next view
        // controller, so we can update our currentIndex to the value we obtained 
        // in the willTransitionToViewControllers method:
        currentIndex = nextIndex
    }
}

请注意，这些方法的第一个参数是pageViewController（UIPageViewController的实例），而不是pageItemController当前代码中的那个。

最后，仅需注意：您引用（UIPageViewControllerNavigationDirection）的枚举仅在setViewControllers(_,

direction:)方法中使用。

以上是 在UIPageViewController中获取用户滑动方向 的全部内容， 来源链接： utcz.com/qa/416912.html

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